Marshall MA 100C 100 Watt All Valve Amplifier

Tube or solid-state, this section goes to eleven!
User avatar
peterc
Information
Posts: 41
Joined: 30 Mar 2010, 18:58
Location: Jozi
Has thanked: 86 times
Been thanked: 3 times
Contact:

Post by peterc »

BB

Awesome post, thanks for that

Peter

User avatar
blackbunny
Resistor Ronker
Information
Posts: 372
Joined: 07 Jan 2011, 07:41
my favorite amplifier: Fender Blackface
Completed builds: Lots of mods to lots of pedals
Location: the garage
Has thanked: 270 times
Been thanked: 108 times

Post by blackbunny »

You are most welcome. The countless hours I spent testing and fixing my 2000 Marshall TSL100 has taught me a lot, some of which I was able to use on Dr Nomis' amp.

One thing it taught me is never buy a Marshall made after 1985. The TSL100 has got to be the worst valve amp I've ever owned, whereas I had a 1982 JCM800 50 watt 4 input Model 1987 that was superb - reliable, great sounding and loud. Wish I still had it, yada yada :slap:

I eventually fitted a JCM800 series 50 watt output transformer to the TSL100, lowered the HT and other power supply voltages with some 10 watt ceramic resistors and now it runs beautifully with 4 x JJ 6V6 output valves fitted for around 44 watts, or I can take the 6V6's out and get a raunchy 50 watts of Brit rage with a pair of EL34S and a change of bias. The primary impedance of the Marshall 50 watt output tranny suits both options beautifully, :applause:

User avatar
DrNomis
Old Solderhand
Information
Posts: 6807
Joined: 16 Jul 2009, 04:56
my favorite amplifier: Self-Built Valve Amp Head :)
Completed builds: Dallas Arbiter Fuzz Face,Tone Bender Professional Mk 3,Tone Bender 3-Knob,Baja BK Butler Tube Driver,Baja Real Tube Overdrive,Roger Mayer Octavia,EH Soul Preacher,Tech 21 XXL Distortion,MFOS Weird Sound Generator.
Location: Darwin,Northern Territory Australia
Has thanked: 98 times
Been thanked: 278 times

Post by DrNomis »

I would like to once again thank Blackbunny for fixing my Marshall amp for me, you're a Legend mate....... :D :thumbsup


I played the amp yesterday and it is still running well without any problems whatsoever.


On other things:


A good mate of mine has left his Peavey Triumph 60 Watt Valve amp with me so I can do some mods to it as suggested by Blackbunny, one of the mods involves changing out the stock screen-grid resistors for higher value ones, the stock screen-grid resistors are 100 Ohm/5 Watt Ceramic Wire-Wound types (going by what I can read on the schematic I was able to find on the internet), Blackbunny's suggested mod is to up the value from 100 Ohms to 220 Ohms, so, I'm going to visit my local Jaycar Electronics store on Monday to buy the needed 220 Ohm/5 Watt Ceramic Wire-Wound resistors, my mate popped-by for a visit yesterday and he gave me all the parts he had ordered online which were needed to do the other mods to his amp, I'll see if I can get some of the mods done later on today, I may even start a new thread about it too.


One other mod that my mate wants to do to his Peavey Triumph amp is to replace the stock 6L6 Power Tubes with a pair of KT66 Power Tubes, I think this will be an interesting mod because I am curious about how the KT66 Tubes will sound, I'm guessing that they will probably have a similar tone to the stock 6L6 Tubes because the 6L6 and KT66 are both what are called Beam-Power Tetrodes, so the transfer-curves should be similar, the amp may need re-biasing after switching over to the KT66 Tubes.

Incidentally, I seem to recall reading somewhere that the Marshall Bluesbreaker Amp used two KT66 Tubes and two 12 Inch Celestion Greenback speakers, or I could be wrong.
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.

User avatar
phatt
Transistor Tuner
Information
Posts: 1224
Joined: 04 Aug 2010, 05:17
Location: Morayfield SE Qld AU
Has thanked: 8 times
Been thanked: 343 times

Post by phatt »

blackbunny wrote:You are most welcome. The countless hours I spent testing and fixing my 2000 Marshall TSL100 has taught me a lot, some of which I was able to use on Dr Nomis' amp.

One thing it taught me is never buy a Marshall made after 1985. The TSL100 has got to be the worst valve amp I've ever owned, whereas I had a 1982 JCM800 50 watt 4 input Model 1987 that was superb - reliable, great sounding and loud. Wish I still had it, yada yada :slap:

I eventually fitted a JCM800 series 50 watt output transformer to the TSL100, lowered the HT and other power supply voltages with some 10 watt ceramic resistors and now it runs beautifully with 4 x JJ 6V6 output valves fitted for around 44 watts, or I can take the 6V6's out and get a raunchy 50 watts of Brit rage with a pair of EL34S and a change of bias. The primary impedance of the Marshall 50 watt output tranny suits both options beautifully, :applause:
LOL, well if you have owned and fixed a TSL100 then you obviously were well qualified to help DrNomis. :applause:

Those TSL100's are a wiring nightmare.
IIRC, 5 pcb's and I stopped counting Conn blocks at around 50. [smilie=thumbdown2.gif]

Even after all the overvoltage problems and bias creep was fixed I did not like the sound. The Amp was extremely brittle when on Ch2 or Ch3 (Jezz my worst SS amp rigs sound more Marshall that that crap)
After much tweaking,,, I found changing the HT for PI made a night and day difference. I settled on 18k/5W.
I may not be the most qualified amp nerd but at 60 I've heard enough REAL Marshall's to know what they Should sound like.

Owner is very happy with the result,, completely different amp now.

Phil.

User avatar
DrNomis
Old Solderhand
Information
Posts: 6807
Joined: 16 Jul 2009, 04:56
my favorite amplifier: Self-Built Valve Amp Head :)
Completed builds: Dallas Arbiter Fuzz Face,Tone Bender Professional Mk 3,Tone Bender 3-Knob,Baja BK Butler Tube Driver,Baja Real Tube Overdrive,Roger Mayer Octavia,EH Soul Preacher,Tech 21 XXL Distortion,MFOS Weird Sound Generator.
Location: Darwin,Northern Territory Australia
Has thanked: 98 times
Been thanked: 278 times

Post by DrNomis »

The thing I like most about my MA100C amp now is how well the clean channel takes pedals, definitely sounds way better than the little Peavey Backstage Plus i had been using while the MA100C was being fixed, I've soon discovered that I'm quite partial to both clean and overdrive amp tones with lots of mids in them, my Gibson USA LP Studio guitar naturally has a lot of mids in it's sound already, but the MA100C seems to accentuate them a bit so I get a classic rock sound.


Yep, mids are where it's at, that's where your loudness frequencies tend to be, and it just so happens that the human ear is most sensitive to midrange frequencies, and the response drops off for lows and highs, that's why you need mids to cut-through in a live band mix.
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.

User avatar
DrNomis
Old Solderhand
Information
Posts: 6807
Joined: 16 Jul 2009, 04:56
my favorite amplifier: Self-Built Valve Amp Head :)
Completed builds: Dallas Arbiter Fuzz Face,Tone Bender Professional Mk 3,Tone Bender 3-Knob,Baja BK Butler Tube Driver,Baja Real Tube Overdrive,Roger Mayer Octavia,EH Soul Preacher,Tech 21 XXL Distortion,MFOS Weird Sound Generator.
Location: Darwin,Northern Territory Australia
Has thanked: 98 times
Been thanked: 278 times

Post by DrNomis »

Hey Everyone,

Thought I would post an update so here it is.


Anyway, it is now December and my Marshall amp has been going strong without skipping a beat or blowing any more fuses ever since I got it back from being fixed...... :D 8)
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.

User avatar
DrNomis
Old Solderhand
Information
Posts: 6807
Joined: 16 Jul 2009, 04:56
my favorite amplifier: Self-Built Valve Amp Head :)
Completed builds: Dallas Arbiter Fuzz Face,Tone Bender Professional Mk 3,Tone Bender 3-Knob,Baja BK Butler Tube Driver,Baja Real Tube Overdrive,Roger Mayer Octavia,EH Soul Preacher,Tech 21 XXL Distortion,MFOS Weird Sound Generator.
Location: Darwin,Northern Territory Australia
Has thanked: 98 times
Been thanked: 278 times

Post by DrNomis »

Update:


It's May of 2018 and the Marshall MA100C amp is still going strong and has not blown a single fuse since my last update, been having a great time playing my new 2014 Fender USA Standard Stratocaster through it, I love my Marshall MA100C amp to bits, it does exactly what i want it to do.

I have to say that those three Genalec Gold Lion Gold-Pin ECC83S Twin Triode preamp valves I installed are definitely sounding really good, they really shine when I'm using the clean channel, the tone is nice and clear, and when you add some of the built-in spring reverb effect it has an almost 3D quality to it, the Overdrive channel sounds great in both crunch and boosted-crunch modes, not really surprising cause they are supposed to be Audiophile-grade ECC83 valves suitable for use in high-end valve audio equipment.


Here's a pic of the Marshall MA100C amp plus my 2014 Fender USA Standard Stratocaster guitar, and a certain furry feline (the cat sitting on the amp), as you can see, they are happily getting along with each other:
Attachments
Marshall MA100C amp, Fender USA Strat, and cat.
Marshall MA100C amp, Fender USA Strat, and cat.
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.

User avatar
DrNomis
Old Solderhand
Information
Posts: 6807
Joined: 16 Jul 2009, 04:56
my favorite amplifier: Self-Built Valve Amp Head :)
Completed builds: Dallas Arbiter Fuzz Face,Tone Bender Professional Mk 3,Tone Bender 3-Knob,Baja BK Butler Tube Driver,Baja Real Tube Overdrive,Roger Mayer Octavia,EH Soul Preacher,Tech 21 XXL Distortion,MFOS Weird Sound Generator.
Location: Darwin,Northern Territory Australia
Has thanked: 98 times
Been thanked: 278 times

Post by DrNomis »

Thought I would post a new update on my Marshall MA100C amp so here goes......

It's looking like I'm going to have to order a full set of new replacement pots for my MA100C amp, reason being is that both of the channel master volumes are sounding a bit crackly when I adjust them, also the presence knob feels a bit gritty when I turn it, and occasionally the amp sounds like it has lost some bass in the tone, so, I'm just going to cut-to-the-chase and order a full set of replacement pots online, I found this website that seems to have them in stock:

https://www.amprepairparts.com/marshall ... QC_oQs2_3E


To be honest, I'm not really surprised that it needs a full set of new pots considering that the amp is most likely already over ten years old now, geez....what a troubled life it's had so far, eh?
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.

Post Reply